MIT researchers create fabric that senses user movements and responds to them
Textile manufacturing may be one of the oldest technologies known to humans, but adapting the achievements of the information age to our clothing has proven difficult. Some attempts, such as Google Project Jacquard, which tried to bring clothing into the modern era, were not particularly successful.
A new type of fiber developed by researchers from the Massachusetts Institute of Technology and Sweden can be used to make clothing that detects how much it stretches or compresses, and then provides immediate haptic feedback in the form of pressure, lateral stretching or vibration.
The team suggests that such fabrics could be used in clothing that helps swimmers during training, athletes control their breathing, and patients recovering from illness or surgery restore their breathing patterns.
The multilayer fibers contain a fluid channel at the center, which can be activated by a special fluid system. This system controls the geometry of the fibers by creating pressure and releasing a fluid, such as compressed air or water, into the channel, allowing the fiber to act as an artificial muscle. The fibers also contain stretchable sensors that can detect and measure the degree of stretching. The resulting composite (multicomponent) fibers are thin and flexible enough to be sewn, woven or knitted on standard commercial machines.
The fibers, named OmniFibers, were presented in October 2021 at an online conference of the Association for Computing Machinery's User Interface Software and Technology symposium. The new fiber architecture has several key features. Its extremely narrow dimensions and the use of an inexpensive material make it relatively easy to structure the fibers into various fabric forms. It is also compatible with human skin, since the outer layer is made of a material similar to ordinary polyester.
The fast response and the variety of forces the fabric can transmit allow the rapid feedback system to be used for training or remote communication using haptic sensations (based on touch). Scientists note that the drawback of most existing artificial muscle fibers is that they are either thermally activated, which can cause overheating when in contact with human skin, or have low energy efficiency or laborious training processes. These systems often have slow response and recovery times, which limits their immediate use in applications requiring rapid feedback.
As an initial test application of the material, the team created a type of underwear that singers can wear to track and reproduce the movement of breathing muscles, and then provide kinesthetic feedback through the same garment to encourage optimal posture and breathing patterns for the desired vocal performance.
MIT research scientist Ozgun Kilic Afsar said: "Singing is especially close to home, because my mother is an opera singer. She is a soprano." During the development and manufacturing of this clothing, the researchers collaborated with classically trained opera singer Kelsey Cotton. They asked the singer to perform in clothing made from their robotic fibers and recorded motion data from strain sensors woven into the fabric. They then converted the data into corresponding haptic feedback.
“In the end, we were able to achieve both the sensations and the actuation methods we wanted in the textile to record and reproduce complex movements that we could capture from the physiology of an experienced singer, and transfer them not to the singer but to the body of a novice. This way, we don't just obtain this knowledge from an expert, we can pass it on to someone who is just learning”
Although this initial testing is taking place in the context of vocal training, the same approach could be used to help athletes learn how to best control their breathing in specific situations, based on monitoring experienced athletes performing various actions and stimulating muscle groups that are "working". Ultimately, there is hope that such clothing could be used to help patients restore healthy breathing after major surgery or a respiratory illness such as coronavirus, or even as an alternative treatment for sleep apnea.
Afsar is doing this work as part of her doctoral dissertation at the Royal Institute of Technology in Stockholm. She explains: "The physiology of breathing is actually quite complex. We don't fully understand which muscles we use and what the physiology of breathing consists of." Thus, the clothing they developed has separate modules for monitoring different muscle groups during the user's inhalation and exhalation and can reproduce individual movements to stimulate the activation of each muscle group.
Professor of Media Arts and Sciences Hiroshi Ishii said he can foresee many applications of this technology: "Everyone has to breathe. Breathing has a big impact on productivity, self-confidence and performance. Breathing is important for singing, but it can also help with recovery from surgery or depression. Breathing is also important for meditation." According to him, the system could be useful for training other types of muscle movements besides breathing.
“Many of our artists have studied amazing calligraphy, but I want to feel the dynamics of a brushstroke, which could be done with a sleeve and glove made from this feedback material. And Olympic athletes could refine their skills by wearing clothing that reproduces the movements of the best athletes, whether a weightlifter or a skier”
The soft fiber composite, which resembles yarn, has five layers:
- the innermost channel for the fluid
- a silicone-based elastomer tube containing the working fluid
- a soft stretchable sensor that detects deformation as a change in electrical resistance
- a stretchable outer braided polymer mesh that controls the external dimensions of the fiber
- an inextensible thread that provides a mechanical limit on overall stretchability
“This study skillfully combines fiber-level engineering and fabric-level design. The work demonstrates various machine knitting techniques, including intarsia and active spacer fabric, an advanced state of the art in embedding actuating fibers into textiles. Integrating strain sensing and feedback is important when we talk about wearables interacting with active fabrics”
The researchers plan to continue refining their fabric, including its control electronics and compressed air supply system, to make it as unobtrusive and even more compact as possible, and to develop a manufacturing system that can produce longer fibers. In the coming months, they plan to begin experiments using the system to transfer skills from an expert to a novice singer, and then to study various movement practices, including choreographers and dancers.
